A beam of parallel rays is brought to a focus | vedclass

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(C) The focal length of a plano-convex lens is $f_1 = f$. The focal length of a thin concave lens is $f_2 = -f$ (since it is a concave lens of the sam

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The focus shifts to infinity

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(C) The focal length of a plano-convex lens is $f_1 = f$. The focal length of a thin concave lens is $f_2 = -f$ (since it is a concave lens of the same focal length).When two thin lenses are placed in contact,the equivalent focal length $F$ is given by the formula:$\frac{1}{F} = \frac{1}{f_1} + \frac{1}{f_2}$Substituting the values:$\frac{1}{F} = \frac{1}{f} + \frac{1}{-f} = 0$Therefore,$F = \infty$.Since the equivalent focal length is infinite,the parallel rays will remain parallel after passing through the combination,meaning the focus shifts to infinity.

$A$ beam of parallel rays is brought to a focus by a plano-convex lens. $A$ thin concave lens of the same focal length is joined to the first lens. The effect of this is:

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